1. Field of the Invention
The present invention concerns a power electronic circuit arrangement for a rotating field machine.
2. Description of the Related Art
Electric drive systems with rotating field machines, especially with permanently excited synchronous machines, have already reached a high state of development. Their advantage is that their high specific force densities allow high starting torques and, at the same time, low weight. In this connection, the efficiencies of the total drive system that are realized in this way and the power density depend to a great extent on the power electronic supply.
Various power electronic circuit arrangements for this are already known from our own in-house prior art. For example, FIG. 1 shows an arrangement in which three phase windings 41-43 of a permanently excited synchronous machine that is connected to a DC voltage source 30 can be controlled independently of one another by means of power electronic functional blocks 10. FIG. 2 shows an arrangement using functional blocks 10, in which the individual phase windings 41-43 cannot be controlled independently of one another.
In this connection, FIG. 3 shows the layout of a functional block 10 from FIG. 1 or FIG. 2 in two-point connection as a so-called half-bridge circuit with two controllable electronic switches 1, 3 and two antiparallel diodes 2, 4. Alternatively, multipoint circuits can also be used. As an example, FIG. 4 shows the layout of a functional block 20 in three-point connection with four controllable electronic switches 1, 3, 5, 7, four antiparallel diodes 2, 4, 6, 8, and two additional diodes 22, 24.
Basic circuits of these types make it possible to operate the synchronous machine both as a motor, in which case electric energy from an external energy store, such as a DC voltage source, is converted to mechanical work in the synchronous machine, and as a generator, in which case mechanical work performed on the synchronous machine is stored as electric energy in the external energy store. To this end, the external store, for example, in the form of a storage battery, can be discharged (motor operation) or charged (generator operation).
This makes it possible, for example, to recover energy during mechanical braking. Likewise, in hybrid systems, the time-variant difference between the power demanded from the drive system and the power made available by an internal combustion engine can be compensated.